44 PEOCEEDINGS OP THE NATIONAL MUSEUM vol.72 



Tremogasterina malleolus, new species, Gulf of Mexico. 



Tremogasterina proUematica Canu, 1911, Rocanean of Argentina. 



Tremogasterina (Poricella) maconnica Canu, 1904, Eocene of Tunis. 



Tremogasterina liorrida Canu and Bassler, 1923, Miocene of Florida. 



Tremogasterina truncatorostris Canu and Bassler, 1923, Miocene of 

 San Domingo. 



Tremogasterina (Galeopsis) convexus Canu and Bassler, 1920, Eocene 

 (Midwayan). 



Tremogasterina (Lepralia) areolata Reuss, 1874, Tortonian of 

 Austria. 



Tremogasterina (Crihrilina) cuspidata Canu and Bassler, 1923, 

 Miocene of Cuba. 



Structure. — We have been able to examine a number of recent 

 specimens provided with their chitinous appendages but unfortunately 

 dried. Never have we been able to see the superior ectocyst as iu all 

 the other escharian bryozoa (Ascophora). On the contrary, through 

 the frontal pores we have always been able to distinguish the subja- 

 cent ectocyst. Moreover, the proximal limit of the opercula being 

 always indecisive, reveals its true nature as an opercular valve 

 attached to the ectocyst. Nevertheless, the anatomical study, after 

 decalcification, of specimens preserved in alcohol is very desirable. 



The calcification of the frontal is very difficult to understand. 

 This frontal is formed essentially by an olocyst perforated in the 

 middle by more or less scattered reniform pores, arranged in triangle 

 or like a rose. The superior pleurocyst begins on the sides and 

 invades almost all the frontal, leaving only in the middle an area in 

 which are the reniform pores. We have not been able to observe 

 young zooecia in formation on the zoarial margins nor have we 

 observed directly the development of the pleurocyst. Smitt, 1872, 

 in studying Tremogasterina mucronata seems to have been more for- 

 tunate, but he is too brief. He remarks: 



As the calcification goes on, at first it fills up the furrows between the zooecia, 

 marking their limits through irregular rows of secondary pores. At last the 

 whole front side of the zooecia is covered by this layer, with the exception of 

 a great hole in their middle into which the above-named lunate pores open 

 themselves. 



The pleurocyst is clearly visible around the peristome and on all 

 the ovicells. Removed from all endocystal elements, at least appar- 

 ently so, its formation is absolutely mysterious. Lang, 1922, has 

 shown an analogous development of secondary tissue in the cribri- 

 morph Tricephalopora group. The chamber thus formed between the 

 ectocyst and the calcified frontal appears to us to be a hypostege in 

 connection with the hydrostatic function; it is a kind of external 

 compensatrix. The entrance of water by the pores permits the 

 extrusion of the tentacles while its exit allows their invagination. 

 While in the other Anasca (Flustrines) the hyposteges communicate 



